CARET is an ongoing double-blind lung cancer chemoprevention trial of the efficacy and safety of the combination of 30 mg beta-carotene and 25,000 IU retinyl palmitate daily in two high-risk populations: (a) male and female current and former smokers recruited primarily from insurance-based sources, and (b) males with extensive occupational asbestos exposure recruited primarily from employment-based sources. We have documented successful recruitment, excellent adherence, and minimal side effects in over 15,000 participants randomized thus far at six study centers. Through 30 April, 1993, CARET has randomized 4,000 asbestos-exposed workers, exceeding accrual goals at all five CARET asbestos centers, and 11, 105 heavy smokers. Seattle and Portland have exceeded their heavy smoker goals, and Irvine is on track to achieve its goal in July 1994. During the final five-year period, CARET will focus on retention, adherence to protocol, ascertainment of endpoints, monitoring of key design parameters, closeout of the trial, and analysis and publication. Projections indicate that with 14,240 smokers and 4,010 asbestos-exposed participants and 114,100 person-years of follow-up through February 1998, CARET will be capable of detecting a 23% reduction in lung cancer incidence in the two high-risk populations combined, and 27%, 49%, 32%, and 35% reductions in the smokers, female smokers, male smokers, and asbestos-exposed subgroups, respectively. The New Haven Center met its goal of randomizing 1,000 participants in November 1992. Through 30 April, 1993 the Study Center has randomized 1,019 asbestos-exposed workers plus 2 heavy smoker spouses. Participants will continue to be contacted by telephone twice yearly and seen at the Study Center annually throughout the follow-up period. Retention efforts will be further emphasized in the final 5-year grant period, including a participant advisory committee and a local newsletter. We will participate in CARET-wide analyses and publications.